The NIV footnote to Jude 1 alerted me to a great example of the challenges of the dative case. The second part of the salutation reads, “To those who have been called, who are loved in God the Father (τοῖς ἐν θεῷ πατρὶ ἠγαπημένοις) and kept for Jesus Christ (Ἰησοῦ Χριστῷ τετηρημένοις).” The NIV goes with “in” for ἐν, although its meaning is not immediately apparent, and it goes with “for” for the dative Ἰησοῦ Χριστῷ. The footnote reds, “Or by; or in.”